Operational Deflection Shape Analysis of an electrically driven fan 

This study investigates the issues surrounding an extraction fan used in a filtration system that handles hot and contaminated air. A significant upgrade of the drive train, increasing its power from 355 kW to 630 kW, required the replacement of both the induction machine and the impeller, resulting in increased size and mass. Subsequent operational problems, primarily destructive cracks in the fan’s impeller, were observed, and motion amplification settings hinted at frame movements related to the drive train. Maintenance efforts confirmed optimal balance and alignment quality but raised suspicions of frame resonance areas causing excessive vibrations. This analysis aims to identify the root cause of drive train problems and provide recommendations for corrective and proactive maintenance. Key machine properties are provided, along with bearing fault frequencies. Vibration measurements recorded frame movements at multiple locations under different operating states, with a deliberate focus on a structural resonance at 1370 RPM. The study seeks to address these issues comprehensively.